1. Field of the Invention
This invention relates to a novel immunogenic steroid-protein conjugate and to its administration to ewes in a flock of sheep to increase the fertility of the flock. By "increasing fertility" is meant increasing the potential of a flock of sheep to multiply by increasing ovulation in ewes.
2. Description of the Prior Art
Increasing the naturally occuring rate at which a flock of sheep will reproduce has long been the object of study. The fertility or rate of multiplication of a species is affected by many factors including the genetic make-up and nutrition of an animal.
It is known that the ovulation rate in sheep may be increased by immunising sheep against certain steroid hormones. It is of great commercial importance to the farming community if the fertility of sheep may be increased effectively and inexpensively to reliably produce increased lambing percentages.
It has been discovered that the immune response system of an animal can be manipulated to affect the oestrous cycle including the ovulation rate.
The use of an immunogenic steroid-protein conjugate has been suggested where the protein is a serum albumin and the effectiveness or rate of administration is critically influenced by the level of steroid binding antibody titre in peripheral plasma before, during and after the mating period.
Such methods are difficult to plan, monitor and control particularly as the relationship between steroid antibody titre and ovulation-rate is obscure.
The object of the present invention is to provide a method of increasing fertility in sheep which is achieved by one or two administrations of an agent to a ewe in a year and which does not require blood level monitoring or sophisticated dosage effectiveness analysis.